The present invention relates to apparatus for wet treatment of running webs of photographic material, e.g., to film processors. More particularly, the invention relates to improvements in apparatus for contacting both sides of a running web of photographic material with a liquid while the web advances lengthwise along a substantially horizontal path.
In many presently known film processors, a web of photographic material which is to be contacted with a liquid medium (e.g., in a developing machine wherein photographic material is contacted by developing, fixing and rinsing fluids) is fed into a chamber by a first pair of advancing rolls and is withdrawn from the chamber by a second pair of advancing rolls. That portion of the web which advances through the chamber is flanked (from above and from below) by plate-like guides which are closely adjacent to each other and have openings for directing streams of liquid against the respective sides of the running web. The configuration of the guides (especially in the region of the inlet for admission of the web into the chamber and in the region of the outlet where the web leaves the chamber) is selected in such a way that both sides of the running web are contacted by identical quantities of liquid as long as the pump or pumps which deliver liquid into the openings of the guides operate at a constant rate. This can be achieved only if the surfaces of the guides are machined with a high degree of precision and if the distance between the guides is selected with a very high degree of accuracy. It has been found that the extremely thin films of liquid at the two sides of a running web will be interrupted in immediate response to deviations of the output of the pump or pumps from a predetermined value. Each and every interruption of a liquid film entails non-uniform contact between liquid and successive increments of the running web, i.e., the exposed film which is treated in such apparatus will be developed at a non-uniform rate with attendant reduction of the quality of developed film frames.
A somewhat different film processor is disclosed in U.S. Pat. No. 4,023,190 granted May 10, 1977 to Fassler. The patentee provides a tank within a reservoir. The tank communicates with the reservoir and contains pairs of advancing rolls with means for sealing the inlet and outlet from the nearest advancing rolls. The sealing means engage the advancing rolls and are subjected to extensive wear. Moreover, the pumping means must circulate large quantities of liquid in order to maintain the level of liquid above the path for the webs of photographic material.